1. Field of the Invention
The present invention relates to an ink jet print head that can eject ink from ejection openings, an ink jet printing apparatus using the ink jet print head, and a method for manufacturing the ink jet print head.
2. Description of the Related Art
In an ink jet printing system, an ink jet print head that can eject ink is used to attach ink droplets ejected by the print head to a print medium such as paper. The ink jet printing system makes only very low noise and enables high-speed printing. The ink jet printing system also enables ordinary paper to be printed. Among such ink jet print heads, those using heating elements as energy generators for ejecting ink have recently been gathering much attention because of the ease with which these print heads enable the integration of a large number of energy generators.
FIG. 12 is a front view illustrating a conventional example of a print head using such heating elements. FIG. 13 is an exploded perspective view of a peripheral part of the print head as viewed from a rear surface of the print head. FIG. 14 is an enlarged sectional view taken along line XIV-XIV in FIG. 12. FIG. 15 is an enlarged view of a rectangular part shown by an arrow XV in FIG. 14. FIG. 16 is an enlarged view of a rectangular part shown by an arrow XVI in FIG. 15.
The ink jet print head comprises an ejection element 1150 provided at its leading end (lower end in FIGS. 12 and 13) as shown in FIGS. 15 and 16. A plurality of ejection openings 1151 (see FIG. 16) are formed between an Si (silicon single crystal) board 1160 and a top board 1165 constituting the ejection element 1150; the plurality of ejection openings 1151 are formed in a line in a lateral direction in FIG. 12, and ink can be ejected from the ejection openings 1151 in the direction of an arrow g. Each of the ejection openings 1151 is in communication with a common liquid chamber 1153 through a corresponding liquid channel 1152. Each of the liquid channels 1152 is provided with an electrothermal converter (heater) 1154 as an energy generating element.
The ejection element 1150 is positioned and bonded on a radiating ceramic plate 1110, on which an electric wiring board 1120 is mounted. The electric wiring board 1120 is electrically connected to the ejection element 1150 by an electric wire 1190.
As shown in FIG. 15, an ink storing chamber 1214 is formed at the bottom of an ink storing case 1200 shown in FIGS. 12 and 13; the ink storing chamber 1214 is in communication with a supply port 1150 in the ejection element 1150. As shown in FIG. 13, a joint case 1300 includes a joint 1219 connected to an external ink supply device (not shown). The joint 1219 comprises an inlet filter 1215 and an outlet filter 1216. A joint cover 1218 is welded to the joint 1219. The joint 1219 and the ink storing chamber 1214 are in communication with each other through pipes 1301 and 1302. The ink storing case 1200 is coupled to the joint case 1300 to construct an ink channel chamber 1210 as shown in FIG. 12.
The ink channel member 1210 is coupled to the ejection element 1150, positioned on the ceramic plate 1110, to construct an ink jet print head.
Ink flows as described below through the print head configured as described above.
Ink supplied by an external ink supply device is introduced into an input joint 1240 from the direction of an arrow a in FIGS. 12 and 13. The ink then flows in the direction of arrows b and c in FIG. 17 while being filtered by the inlet filter 1215. Further, the ink flows from the direction of an arrow d in FIG. 18 through a pipe 1301 into the ink storing chamber 1214. FIG. 17 is an enlarged plan view of a portion on which the joint cover 1218 in the joint case 1300 is mounted. FIG. 18 is a sectional view taken along line XVIII-XVIII in FIG. 17. Ink ejected by the print head is supplied from the ink storing chamber 1214 to the interior of the common liquid chamber 1153 along the direction of an arrow e in FIGS. 15 and 16. The ink is introduced into the liquid channel 1152 along the direction of an arrow f.
Ink not supplied from the ink storing chamber 1214 to the common liquid chamber 1153 flows through the ink storing chamber 1214 in the direction of an arrow h in FIG. 13. The ink flows through the pipe 1302 and through the outlet filter 1216 from the direction of an arrow i in FIG. 18. The ink flows in the directions of arrows j and k in FIG. 17 and through the output joint 1245. The ink is then discharged in the direction of an arrow l in FIG. 18 and returned to the external ink supply device. The ink returned to the external ink supply device is supplied to the print head again. Such ink flow causes bubbles in the ink storing chamber 1214 to be washed away from the print head. Consequently, the print head can always eject ink optimally.
However, the conventional print head described above may present the following problems.
(1) The speed at which the ink jet print head ejects ink depends directly on the performance of the printing apparatus. To improve the ink ejection speed, it is necessary to smoothly supply ink to the interior of the common liquid chamber 1153 and liquid channel 1152. The directions of the arrows e and f in FIG. 16 directly affect the ink supply. Further, the area of the inlet filter 1215 must be increased.
However, an increase in the area of the inlet filter 1215 correspondingly increases the size of a joint portion of the joint case 1300. This increases the size of the whole print head. Further, the ink flow from the joint case 1300 into the common liquid chamber 1153 is bent to offer a large flow resistance to the ink flow. Thus, with a high driving frequency with which ink is ejected, the ink supply may be delayed to preclude the ink from being ejected.
(2) The print head has a large number of joining portions formed by the ink channel and which must be inspected. This degrades the efficiency of assembly operations. The joining portions include, for example, the thermally welded portions between the joint case 1300 and the filters 1215 and 1216 and the joining portions of the pipes 1301 and 1302, which communicate between the ink storing chamber case 1200 and the joint case 1300.